Implications for management and conservation of the population genetic structure of the wedge clam Donax trunculus across two biogeographic boundaries.

Amandine D Marie,Evgenia Karapatsiou,Louis Bernatchez,Ciro Rico,Christophe Lejeusne,Enrique Macpherson,Pilar Drake,José A Cuesta

doi:10.1038/srep39152

Abstract

In a resource management perspective, the understanding of the relative influence of the physical factors on species connectivity remains a major challenge and is also of great ecological and conservation biology interest. Despite the overfishing threat on the wedge clam Donax trunculus in Europe, relatively little information is known about its population genetic structure and connectivity and their consequences on conservation policies. We employed 16 microsatellite loci to characterise the genetic diversity and population structure of D. trunculus. A total of 514 samples from seven different localities along the Atlantic-Mediterranean transition, from the Atlantic (Gulf of Cádiz) to the north-western Mediterranean were genotyped. The analysis of the population genetic structure displayed a clear distinction along the Atlantic-Mediterranean transition with different clusters in the Atlantic Ocean, the Alboran Sea and the northwestern Mediterranean. Consequently, we recommend that these three areas should be considered as different management units. We showed that all populations seem to be at high long-term risk of extinction with the exception of the protected Doñana National Park population which still seems to have evolutionary potential. Therefore, our results emphasized the necessity of protection of this economic resource and the validity of molecular tools to evaluate the population dynamics.

Highlights

In a resource management perspective, the understanding of the relative influence of the physical factors on species connectivity remains a major challenge and is of great ecological and conservation biology interest
Many soft and hard faunal barriers to dispersal have been identified in marine environments throughout the world, including, for instance, the Isthmus of Panama[1,2,3] and the Terminal Tethyan Event[4,5] as hard barriers, as well as the East Pacific Barrier[6,7] and the Benguela upwelling[8] as soft barriers
The wedge clam, Donax trunculus (Bivalvia: Donacidae), is an Atlanto-Mediterranean warm-temperate species found in the Black Sea, the Mediterranean Sea[20] and from Senegal to the northern Atlantic coast of France[21]

Summary

Introduction

In a resource management perspective, the understanding of the relative influence of the physical factors on species connectivity remains a major challenge and is of great ecological and conservation biology interest. Strong genetic differentiation between Atlantic and Mediterranean populations has been shown in fish as well as in shellfish species with contrasting life histories[10,17,18] To explain this phenomenon, two mains factors have been proposed: 1) the one-way surface current of Atlantic water flowing through the Strait of Gibraltar into the Mediterranean[19] and, 2) the presence of a front of surface waters between Almeria in Southeast of Spain and Oran in Algeria, the so-called Almeria-Oran front (AOF)[16]. Two mains factors have been proposed: 1) the one-way surface current of Atlantic water flowing through the Strait of Gibraltar into the Mediterranean[19] and, 2) the presence of a front of surface waters between Almeria in Southeast of Spain and Oran in Algeria, the so-called Almeria-Oran front (AOF)[16] These factors could represent a barrier to gene flow between Atlantic and Mediterranean populations and be responsible for the reduced migration observed. Landing data are only available since 1972 and fishermen were not obliged to declare their catches until 199823, the species has been intensively exploited over the last decades using primarily either artisanal hand-operated dredges in shallow water or commercial boat-operated dredges from subtidal to deeper waters[24]

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